At present, using welds to connect two ends of metal cords is avoided as much as possible. This is since metal cord welds create an inflexible zone in the metal cord, disturbing e.g. the bending of the metal cord. Further, the weld in the metal cord creates a weak zone as far as mechanical properties such as tensile strength are concerned. The force at rupture of a welding zone of a cord is usually less than 60% of the force at rupture of the metal cord without the welding zone.
Another important aspect is noticed when several metal cords are used e.g. to reinforce a timing belt or for use in elevator belts. When one metal cord breaks during load, this seems to create a “shock-effect” or “cascade effect”, which usually causes break of all adjacent metal cords, or even the whole belt. The same applies when several windings of a metal cord are used to reinforce e.g. endless belts. This is another reason why no welds are allowed in these applications.
An other disadvantage of the inflexible zone of the weld, using metal cords in polymer or rubber matrices, is that at the welding zone, due to the inflexibility of the weld, the weld tends to migrate in the polymer or rubber in a transversal direction when the metal cord is bend. This may cause shearing of the matrix.
Avoiding the welds of cords is obtained by demanding predetermined lengths for the metal cords without welds to be supplied. This specified length causes a significant price increase of the metal cords. The metal cord manufacturer faces a waste increase, since insufficient lengths of metal cords or intermediate products cannot be sold or used.